1. Field of the Invention
The present invention relates to oil-filled protectors for use with submergible electric motors and, more particularly, for use with electric submergible motors to be suspended within wellbores.
2. Description of Related Art
Electric submergible pumping systems are widely used throughout the world for recovering subterranean fluids from wellbores to the earth's surface. In many wells, there are deleterious fluids that can chemically attack the materials used in the motor. For example, hydrogen sulfide will chemically attack the copper used in the motor's windings. If these deleterious fluids are not prevented from entering the motor, then the motor will prematurely fail.
For the long term successful operation of such submergible pumping systems, the electric motor must be supplied with uncontaminated cooling motor oil. This cooling oil is partially contained within one or more elastomeric bags within a motor protector. The elastomeric motor protector bags are generally cylindrical in shape and are sealed within an oil filled housing. The bags are filled with oil at the time of installation to an expanded state. With the rise of temperature caused by the immersion in the wellbore, as well as the thermal expansion caused by the operation of the electric motor, the bags tend to slightly expand even more. When the electric motor is turned off, the cooling oil cools and contracts. This contraction allows the motor protector bag to slightly deflate. The elastomer typically used for the elastomeric bags is a saturated nitrile.
A problem encountered is that several deleterious fluids can easily pass through the elastomeric bags and enter the cooling oil, and then attack the motor windings and other internal components. As used herein the term "deleterious fluids" means any liquid or gas that has a chemical reaction with or some other interaction with one or more of the internal workings of the motor that degrade the performance of the motor. Examples of such deleterious fluids are hydrogen sulfide (H2S), carbon dioxide (CO2) and methane (CH4). There is a need for a protector that has the needed elastic properties and at the same time can prevent the passage of such deleterious fluids.